According to Dev Team blog, redsn0w allows owners of A4+earlier devices to install rocky-racoon two different ways:

backup/restore method similar to Absinthe and cinject

its traditional limera1n-based ramdisk install. If you have a lot of media on your A4 device (music, movies, TV shows, etc), then the ramdisk method is preferrred because it avoids any possibility of later problems related to syncing to iCloud (including Photo Stream and Music Match). The ramdisk method is not available for A5 devices or later because limera1n can’t be used. If you’d like to use redsn0w’s ramdisk method, just be sure to put the A4 device in DFU or Recovery mode before starting redsn0w (otherwise it will immediately start to use the backup/restore method).